https://{instanceId}.agent37.app, with the same sk_live_ key sent as the X-Agent37-Key header. See Instance and preview URLs.
Health
GET /v1/health returns { "ok": true, "agent": "hermes", "healthy": true, "hermes": true }. ok is true whenever the gateway is up; agent is the harness that was probed, and healthy reports whether that harness behind it is reachable. By default it probes the instance’s configured harness; pass ?agent=, hermes or openclaw, to probe a specific one (an unknown value is 400 validation_error, and an empty value is the same as omitting it). An unreachable or unprovisioned harness reports as healthy: false with a 200. When Hermes is probed, the body also carries a hermes field mirroring healthy, kept for backward compatibility; other harnesses omit it. Use it as a readiness probe after create or start: the create call returns as soon as the instance’s computer is up, while the agent inside is still booting.
Version
GET /v1/version returns the gateway build, e.g. { "name": "agent37-gateway", "version": "0.1.3" }.